Hi Ghanshyam, thanks for your answer.
I check the VPN, it runs ok. Is not specially fast, but it always works.
The error is always the same: If I include a file of 2 mb or bigger, the process fails, and it fails in the remote server (the configured as TARGET in the replication job), which is closing the port (or at least that is what i understand from the error i get).
Do you think that there is any configuration, either at Alfreco level, Tomcat level, or even at OS level (Debian Linux is the one in the TARGET server) that could be closing the port?
Regards